More magic stones and hockey pucks

[simon7000]

Yes I knew that. If I shift my coffeetable 1 foot it changes the room acoustics and sometimes I can hear it.
Anybody need an acoustic cancellation coffeetable? Just $12.000 (plus shipping).
My point is that the description is there to encite me to buy it. So, I read the description and conclude that it's bogus. YMMV.

jan

And from the description that is a reasonable conclusion! What made it interesting is the good reviews suggest there may be something there. JC provided a hint as to what may be going on mentioning turning on and off the oscillator. If piezo tweeters actually still had ultra-sonic output I would have done a quick test. (The last batch I measured rolled hard at 10K!)

I think the idea of adding bias not just to the air but actually to the tweeters output may be an interesting experiment. I am too backed up to try something today. But how hard is it for anyone to mix in a test oscillator with an existing music system?

As I said before sometimes an outlandish idea actually works. (I reserve the right to claim magic boxes work after I have actually tried a few things.)

Now as to magic rocks... there may be an explanation, but the smart money would not bet on it.

 

[jcx]

is it really wise to dismiss magic stones on Valentines Day?

 

[Steve Eddy]

At room temp, air molecules are moving at about 450m/s...

Hogwash!

If that were the case, the air molecules would rip the flesh from our bones.

se

 

[SY]

They do that routinely.

 

[auplater]

David Pace - Mean Free Path of Air
http://www.uccs.edu/~tchriste/courses/PHYS549/549lectures/gasses.html

 

[Magura]

David Pace - Mean Free Path of Air
Kinetic Theory of Gasses

I think we have been over this before, haven't we?
Quit bringing facts to the table, it's no good you know.

You might as well try to prove to the pope, that Jesus is a fictional character.


Magura

 

[simon7000]

is it really wise to dismiss magic stones on Valentines Day?

I strongly suggest you try a heart shape box of good chocolate candies. If that doesn't work then the application of a magic rock to her head might, but there are serious legal complications! So stick to chocolate.

 

[vacuphile]

Should we give back New York city? The guys who took the beads weren't even of the right tribe?

So you sense the Dutch are not the right tribe?

 

[jneutron]

While I did not read the floobydust explanation on the vendor site, I have a simple question.


Why is it nobody's talking about the impact ultrasonic energy at those levels has on the cilia? Not cilia small enough for 40Khz, but dithering of the audio band hairs?

jn

 

[SY]

I'm more concerned about my dog.

But you assume there's ultrasound. That was sheer speculation several steps removed from an offhand comment on a secondhand observation.

 

[jneutron]

I'm more concerned about my dog.

But you assume there's ultrasound. That was sheer speculation several steps removed from an offhand comment on a secondhand observation.

Ah, fair enough.

It looked like U/S was somehow involved from the later posts from the posts... If not, oh well...

jn

 

[simon7000]

So you sense the Dutch are not the right tribe?

Those were the guys giving the beads out. The other party selling actually had no property rights!

 

[scott wurcer]

At room temp, air molecules are moving at about 450m/s, so I think we're safe to assume that there's no stiction (presumably against the luminiferous aether or the phlogiston).

That checks, my references give the particle velocity at 87dB SPL (@1kHz A weighting is irrelevant) as about 1.1mm/s.

 

[tomchr]

I'm more concerned about my dog.

I have noticed that when I perform amplifier testing at above 10 kHz with a speaker connected rather than the usual dummy load, all the neighborhood dogs start barking. It's really quite entertaining in a mad scientist sort of way...

I still Cal has the right idea, though. Just place a couple of hockey pucks at various locations in the room. I actually have a stack of five hockey pucks below my stereo. The sound just wouldn't be the same without them...

~Tom

 

[vacuphile]

Non linearity of air AFAIK only plays a role at very high (close to 200 dB) intensities. The opposite situation from tape bias.

 

[vacuphile]

Those were the guys giving the beads out. The other party selling actually had no property rights!

Not beads actually, but bought it for 5 dozen guilders. Of course, that was before the Euro, so it is actually a bit more than you would expect. You see, this tribe contains some clever traders, always in for a bargain. But even then, we didn't want to rip off folks just because they had no paper, and hence no property rights..

You guys could have bought your way to the West, think about it.

 

[revboden]

Yes, but what you all are not accounting for was the extremely high Guilder to Squaw exchange rate

 

[DF96]

Technically it works with capacitively activated crystals.

That sounds to me like an attempt to describe an ordinary ultrasonic transducer, but in a way which makes it sound advanced and expensive.

 

[simon7000]

Non linearity of air AFAIK only plays a role at very high (close to 200 dB) intensities. The opposite situation from tape bias.

Air would be nonlinear in the 200db range as that requires complete atmospheric modulation. Of course since we wouldn't survive it, that probably is not an issue.

 

[scott wurcer]

Non linearity of air AFAIK only plays a role at very high (close to 200 dB) intensities. The opposite situation from tape bias.

Above 194dB or so propagation is by shockwave, air has nonlinearity well below this but it becomes a complex thermodynamic problem. They estimate the two major volcanic catastrophies at 300+ dB. The AES reprints have an article on the 180+dB horns used to test launch pad design.